Polymer-Based Gas Sensors

The flexibility of polymers properties is attained at the expense of doping and the introduction of functional additives (see Chaps. 13 and 24 [Vol. 2]). Polymers can have either electronic or ionic conductivity when conductivity is controlled by migration of ionic species. This means that polymers 

NHj Optical PAni-PMMA Sensitivity of PAni-PMMA coatings is 10-4, (XX) ppm, reversible response 

NOj Conductometric PAni-isopolymolybdic acid nanocomposite Resistance increases with NO, concentration 

NO Amperometric Polydimethylsiloxane (PDMS) Shows sensitivity to 20 nM gas, high performance characteristics in terms of response time and selectivity 

QCM-type Amino-functional poly(styrene-cochloromethyl styrene) derivatives DPEDA functional copolymer with 5 wt% of siloxane oligomer shows 11 min response time and good reversibility even near RT (50 °C) 

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Lepcsenyi I, Reichardt A, Inzelt G, Harsanyi G (1999) Highly sensitive and selective polymer based gas sensor. In Proc 12th European Microelectronics and Packaging Conference, Harrogate, UK, 7 9 June 1999, pp 301 305 Inzelt G (2000) Electrochim Acta 45 3865... 

Mechanisms of Conductivity Change in Polymer-Based Gas Sensors. 129... 

There have been attempts to use metal oxide-CB composites for gas sensor design (Liou and Lin 2007). However, such an approach does not give any improvement in operating characteristics in comparison with conventional metal oxide or CB-polymer-based gas sensors. 

It should be noted that, in contrast to the measure of the magnitude of sensor response, there is no single indicator for stability, and for this reason most reports on stability of polymer gas sensors employ different measures and different experimental conditions. It is thus impossible to compare stability reports directly due to the differences in materials, conditions, data acquisition, etc. Therefore, in this chapter, the analysis of polymer-based gas sensor s stability will be only general. 

Strong water vapor influence (see Figs. 3.14 and 3.15c) is one of the main disadvantages of polymer-based gas sensors, because water vapor is the most common interferant for gas sensors operating at room temperature (Buchler and Ryan 1997 James et al. 2005 Pejcic et al. 2007). For example, Kaplan and Braham (1998) showed that an e-nose based on polymer gas sensors lost sensitivity in the presence of water vapor. Therefore, when humidity levels are not compensated for or controlled, it is possible that the humidity is responsible for some successful discriminations. For example, the... 

One can consider as a disadvantage the low selectivity of polymer-based gas sensors. However, not only the sensors based on conducting polymers but also the other sensors, including sensors designed on the base of metal oxides and many other sensing materials, face this problem. 

Buchler MG, Ryan MA (1997) Temperature and humidity dependence of a polymer-based gas sensor. Proc SPIE 3082 40-48. http //enose.jpl.nasa.gov/publications/sensors/97-0482.pdf Cabala R, Meister V, Potje-Kamloth K (1997) Effect of composite doping on sensing properties of polypyrrole. J Chem Soc Faraday Trans 93 131-137... 

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